js 滚动加载iframe框中内容

    var isIE6 = !!window.ActiveXObject&&!window.XMLHttpRequest;

    //滚动加载
    var scrollLoad =function(){
        $("#content iframe[_src]").each(function(){
                var t = $(this);
                if( t.offset().top<= $(document).scrollTop() + $(window).height()  )
                {
                    t.attr( "src",t.attr("_src") ).removeAttr("_src");
                }
        });//each E
    }

    scrollLoad();
    $(window).scroll(function(){ 
        if(isIE6){ btb.css("top", $(document).scrollTop()+30) }
        //scrollLoad();
    });

<iframe allowTransparency="true" scrolling="no" _src="demo/iframe/2.0-focus-iframe.html?&fade&true" frameborder="0"></iframe>